Enzymes And ATP

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Enzymes and ATP

Enzymes act as protein catalysts in
biochemical processes
Enzymes bind to a substrate and forms the enzyme substrate complex.

Enzymes work by lowering the energy of activation.
Activation energy must be supplied for the reaction to begin, once supplied, the reaction can proceed on its own.
Enzymes can speed up events.
They are not used by during the reaction because the enzyme stays the same, it does not change during the reaction.

(Hudon-Miller, Enzymes, 2013)

Enzymes act as protein catalysts in
biochemical processes


Frutokinase is the enzyme that acts on fructose in the liver and turns fructose into fructose 1 phosphate.



Fructose 1 phosphate is changed to DHAP and glyaraldehyde by an enzyme called aldolase B.

(Hudon-Miller, Enzymes, 2013)

Deficiency in aldolase B is
responsible for HFI


When aldolase B is deficient it can no longer take its substrate fructose I phosphate into DHAP and glyceraldehyde



Fructose can no longer enter glycolysis or gluconeogenesis so can no longer be used as energy



Phosphate is depleted because frutokinase still makes fructose I phosphate



The ability for the electron transport chain to make ATP goes down which can cause liver damage and liver failure



Glucokinase stays in the cytoplasm and glycogenolysis and gluconeogenesis slow down causing hypoglycemia



Symptoms involved with HFI have to do with hypoglycemia, including, shaking, irritability, and lightheadedness.

(Sanders, Hereditary fructose intolerance, 2013)

Lock and key model of enzymatic
activity diagram

(Slitcher, 2012)

Activation Energy Diagram

(Wolfe, 2000)

Defect of aldolase B


The specific substrate acted on by Aldolase B during the
metabolism of fructose is fructose I phosphate.



Fructose I phosphate cannot be turned into DHAP and
glyceraldehyde by aldolase B



This cause the inability for fructose to be used as energy



Due to this fructose I phosphate builds up and phosphate is
depleted

(Sanders, Hereditary fructose intolerance, 2013)

Role of aldolase B in the
metabolism of fructose


Aldolase B take fructose I phosphate and makes DHAP and
Glyceraldehyde.



DHAP and glyceraldehyde can continue down glycolysis to
pyruvate and either make ATP or go to fatty acid synthesis.



Or DHAP and glyceraldehyde can go through gluconeogenesis and make G6P and turn it into glycogen

(Sanders, Aldose B, 2013)

Hypothetically what would happen if the entire Cori
cycle were to occur and remain within that single
cell


If the entire Cori cycle were to occur and remain within a muscle cell, the muscle would not be able to survive



In muscles, glucose is converted to lactate which produces 2 ATP



In the liver, lactate is converted back to glucose and the liver uses 6 ATP



Since the muscles are anaerobic, they are unable to produce their own ATP.



If the lactate stayed in the muscle cell, it would not have enough ATP to sustain itself
(Hudson-Miller, Cori Cycle, 2013)

Entry to the citric acid cycle

(Hudson-Miller, Citric acid cycle: Central to aerobic metabolism, 2013)

Cycle

(Hudson-Miller, Citric acid cycle, 2013)

Electron Transport Chain

(Sanders, Electron transport chain, 2013)

Hypothetical Enzyme Defect


If the enzyme succinate dehydrogenase were defective….



FADH2 would not been made



The rest of the citric acid cycle would be affected



However, do to this enzyme being defective, it will also affect the action of the electron transport chain.



FADH2 is needed to give electrons to complex II, which in turn gives the electrons to complex III, which gives the electrons to complex IV, which uses those electrons to give to oxygen to make water



If succinate dehydrogenase were affected, ATP production will decrease
(Sanders, Electron transport chain, 2013)

Coenzyme Q10...
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